add layer_building etldoc comments

layers/building/building.sql

@@ -1,11 +1,20 @@
+
+
+
+-- etldoc: layer_building[shape=record fillcolor=lightpink, style="rounded,filled",  
+-- etldoc:     label="layer_building | <z13> z13 | <z14_> z14_ " ] ;
+
 CREATE OR REPLACE FUNCTION layer_building(bbox geometry, zoom_level int)
 RETURNS TABLE(geom geometry, osm_id bigint, render_height numeric) AS $$
     SELECT geometry, osm_id,
     least(greatest(3, COALESCE(height, levels*3.66,5)),400)^.7::int AS render_height
     FROM (
+
+        -- etldoc: osm_building_polygon_gen1 -> layer_building:z13
         SELECT osm_id, geometry, height, levels FROM osm_building_polygon_gen1
         WHERE zoom_level = 13 AND geometry && bbox AND area > 1400
         UNION ALL
+        -- etldoc: osm_building_polygon -> layer_building:z14_
         SELECT osm_id, geometry, height, levels FROM osm_building_polygon
         WHERE zoom_level >= 14 AND geometry && bbox
     ) AS zoom_levels